The Texas-based oil and natural gas company's shares began trading Friday on the New York Stock Exchange under the ticker symbol "ATHL."

Athlon priced its offering of 15.8 million shares of its common stock at $20 per share, raising $315.8 million. The IPO price was at the high end of the expected $18 to $20 range. By midday its stock was up $7.09, or 35.5 percent, to $27.09.

The company said it plans to use the proceeds from the offering to repay debt, provide cash for use in its drilling program and for general corporate purposes.

Athlon gave underwriters an option to buy up to nearly 2.4 million additional shares to cover over-allotments.